Swiss Pat. No. 333 144 describes a dobby mechanism in which a reading needle which controls a heddle frame alternately reads control points from two adjacent rows on a pattern card, and thus reads consecutively the even and uneven picks. For this purpose, all reading needles are supported in a guide which carries out, during each lifting operation of the needles and the indexing of the drive cylinder of the pattern card, a lateral back-and-forth movement.
The lifting of the needles from the pattern card, the movement of the needle guide member, and the indexing of the card cylinder must occur, particularly in high speed dobbies, in an extremely small amount of time, whereby all such movements must be tuned satisfactorily to one another.
It is known to control the needle guide member, for example through a wobble plate. The need for space and for lubrication of the wobble plate which is read by a roller is significant. Also, it is possible for oil to be sprayed away from the wobble plate, as a result of which the pattern card can become dirty. Furthermore, considerably high specific stresses of the utilized material and a corresponding wear is created at the contact point of the roller on the roller path of the wobble plate.
A primary purpose of the invention is thus to overcome these disadvantages with a simple, compact and precisely operating apparatus.